Furnace damper control



Nov. 11, 1952 c. F. ALBAN ETAL 2,617,595

FURNACE DAMPER CONTROL Filed Jan. 12, 1951 5 Sheets-Sheet l INVENTORSC/arence FA/bcm 3 Fi'gml. M0 H. Mofzheu/s.

Attorneqs.

C. F. ALBAN ET AL FURNACE DAMPER CONTROL.

Nov. 11, 1952 3 Sheets-Sheet 3 Filed Jan. 12, 1951 "NIH.

INVENTORS C/orence FA/bon 5 Raymond H Mofthews." BY

M 7M Azforne Patented Nov. 11, 1952 Matthews, Detroit, Mich, a'ssignorsto W; M. Chace Company, Detroit, Mich, a. corporation of MichiganApplicat'ionJanuar-y 12, 1951,.SerialN o.'205,717

This invention relatesto a furnace damper control.

It is an object of thisinvention to produce a damper control forfurnaces which automatically opens the damper when the need for heatarises and automatically closes the damper when the heat requirement hasbeen satisfied. i

The invention contemplates an automatic control of this type which is ofsimple structure, efficient and reliable in operation, and which iseconomical to produce.

In the drawings:

Fig. l is a side elevation showing the instant furnace damper control.

Fig. 2 is a plan view of the same.

Fig. 3 is a wiring diagram of the furnace damper control. V

Fig. 4 is a side elevation of a modified form of the instant furnacedamper control, and

Fig. 5 is a bottom plan view of the same.

Referring more particularly to the drawings, it will be seen that theinstant control comprises a lever I pivoted on a fixed support 2 by pin3. A mercury switch 4 is "fixed on arm I by bracket 5. One end of leverI has a cross arm 6 affixed thereto. Apair of spiral torsion springs Iand B have their inner ends secured in the slotted ends 9 of rod l whichis supported at its opposite ends in openings I I in fixed posts l2. Setscrews I3 are threaded in tapped openings in posts I2 and bear againstrod Ill to hold it against rotation. The free ends 14 of springs I and 8bear against the reduced ends I and arm 6 has bias arm 6 downwardly. Inother words, springs I and 8 act at all times against arm 6 and tend torotate lever I in a counterclockwise direction as viewed in Fig. 1. Ifno load were applied on arm I to the right of fulcrum 3. then arm Iwould be held in the position shown in Fig. l by springs 1 and 8.However, lever arm I is connected by draft link or cable I6 with thelower end of damper I'I. Link I6 is connected to arm I as at I8 and todamper IT as at l9.

For purposes of description and not by Way of limitation, damper II,which is the means for controlling the draft on the furnace or thecombustion chamber therein, is shown as a pivoted damper pivotallysupported as at 2!! upon furnace 2|. Damper I'I controls the flow of airinto the furnace and through the grate supporting the coal, wood, orother combustible material being burned in the furnace. The torsionexerted by spring ends I4 on the lever I, the lengths of the power armand the resistance arm of the lever I, and the downward thrust exertedby damper 4 Claims. (01. 236-68) H are coordinated so that the torsionexerted by springs Hon arm 6 will be insufiicient to open temperaturethe arcuate strip 22 will contract.

Heat is supplied to the bimetal strip 22 by an electrical resistanceelement 23. The one end 24 of element 22 is fixed to block 25 by meansof screws 26. Block 25 is fixed on rod In by a set screw '21. Since theend 24 of element 22 is fixed or. anchored, therefore upon a rise intemperature the other end 28 of the arm will move downwardly. Theposition of the bimetal element 22' when the heater 23 is deenergized isshown in Fig. l. A heat responsive latch or holding mechanism isprovided for holding the lever l in its damper open position,illustrated in Fig. '1, full lines. This latch takes the form of athermostatic laminated metal member or strip 29 anchored by screws 30 topost 3| which is fixed on support member 32'. Support member 32 isprovided with an opening 33 through which link I 6 passes. Strip 29,like strip 22, can be made from any known laminated thermostatic metalsuch as bi'e or trimetal. Latch29 is energized by an electricalresistance heating element 34 which is mounted thereon and in heatexchange relation therewith.

The wiring diagram for the instant furnace damper control is shown inFig.. 3. The transformer 35 is connected into the usual volt circuit 35.Thesecondary winding 31 of the transl formerwhich lowers the voltage toany desirable lowvoltage, e. g.,- approximately 24 volts, is connectedthrough thermostat 38 and mercury switch 4 with heating elements .23 and34'. Heating element 23 for bimetal strip 22 will preferably have asubstantially greater heating capacity or wattage than heater 34.Mercury switch 4 is a single pole, double throw switch. Heater 23 isconnected with contact 39 by line 4B and contact 4| is connected byline42 with the secondary winding 31. Theother set of contacts 43 and 44 ofmercury switch 4 are connected respectively by 3 line 45 with heaterelement 34 and by line 46 with the secondary winding 31 of thetransformer through thermostat 38.

The operation of the instant furnace damper control is as follows: Asshown in the dotted lines in Fig. 1, the damper I9 is closed, heatingelements 23 and 34 are deenergized so that latch 39 is in releasedposition, dotted line showing Fig. 2, and heat motor 22 is deenergizedand in contracted position, shown in Fig. 1. Lever arm I is also in thedotted line position shown in Fig. 1 so that the mercury in switch 4 isbridging contacts 39 and M and contacts 43 and 44 are open. Whenthermostat 3B closes and calls for heat, then heater element 23 isimmediately energized and heats bimetal element 22 causing the same toopen, that is, end 28 moves downwardly and acts upon lever arm 6 toswing lever I counterclockwise thereby acting through link I6 to opendamper IT. The counterclockwise movement of lever I is assisted bycounterbalancing springs I and 8. As lever arm I swingscounterclockwise, mercury switch 4 swings with the lever I and themercury in the switch now shifts to the other end of the bulb therebybreaking contacts 39 and M and closing contacts 43 and 44. Thisdeenergizes heating element 23 and energizes heating element 34 so thatlatch or bimetal element 29 now deflects toward the left, Fig. 2, andbeneath the outer end 50 of lever I. Heater element 34 remains energizedas long as thermostat 38 calls for heat. Although heating element 23 isdeenergized when arm I is swung counterclockwise to open damper I'I, itwill be appreciated that heat motor 22 does not cool immediately so thatheat motor 22 acts to hold lever I in the full line position for asufficient length of time to permit latch 29 to swing inwardly beneathend 50 of lever I to hold the same in raised position. This condition ofthe electrical circuit is illustrated in Fig. 3.

Even though thermostatic switch 38 is closed, contacts 39 and M areopen, heating element 23 is deenergized and bimetal strip 22 begins tocontract and finally reaches its fully contracted position, as shown inFig. l. The increased draft through the furnace causes it to supplyadditional heat and as soon as the space being heated reaches thetemperature setting of the thermostat, thermostatic switch 33 opensthereby stopping the current flow through heating element 34. Bimetalelement 29 now begins to cool and flex outwardly toward the dotted lineposition Fig. 2, where it releases the outer end 53 of lever I so thatthe damper II closes and swings arm I clockwise to the dotted lineposition shown in Fig. 1. This again tilts mercury switch 4 so thatcontacts 39 and 4I are again bridged by the mercury in bulb 4 andcontacts 43 and 44 are open.

The form of control shown in Figs. 4 and differs from the principal formof the invention primarily in that the lever arm I is pivotally mountedon supports 5I which depend from support 52 and springs I and 8 and heatmotor 22 and 23 are mounted upon supports 53 which depend from support52. In this form of the invention the holding latch for engaging end 50of lever I comprises a bimetal strip 54 having its end 55 turned at aright angle to provide a hook for engaging beneath the end 50 of leverI. Strip 54 is heated by the heating element 34 the same as bimetalstrip 23. The latch 54 is anchored by screws 53 to fixed support 51.

The electrical circuit or wiring diagram and the mode of operation ofthis furnace damper control is the same as that of the principal form ofthe invention. When thermostat 38 calls for heat and heat motor 22, 23has opened the damper by rotating lever I to the full line position Fig.4, then the circuit through heater 34 is completed and latch 54 flexesinwardly so that hook 55 engages beneath end 50 of lever I to hold leverI in damper opening position until the thermostat 38 is satisfiedwhereupon resistance element 34 is deenergized and latch 54 flexesoutwardly, dotted line showing Fig. 5, to release lever I and permitdamper I! to close.

The electrical circuit diagram, Fig. 3, corresponds with the full lineshowing of the damper control Fig. 1 wherein the damper is opened, end53 of lever I is supported upon latch 29 and the circuit through heatingelement 23 and contacts 39 and M has been broken long enough for bimetalelement 22 to cool to its normal deenergized position. When heat motor22, 23 is energized to open damper H, the circuit through contacts 39,4| will break as the damper I'I approaches fully open position. However,since the resistance element 23 will be covered with insulation in amanner well known, the residual heat in the heat motor will causeelement 22 to expand somewhat further to raise the end 53 of lever Iabove latch 29 and hold the lever 5I in this position until element 29is deflected beneath lever 1 due to the heating of element 34. Afterlatch 29 engages beneath end 50 of lever I, element 22 will contract asits temperature falls but the damper I I will be retained open by latch23 until the thermostat 33 is satisfied and opens to break, the circuit.

It is evident from the above that in case of power failure damper I!will always close and shut off the draft to the furnace.

We claim:

l. A furnace damper control mechanism comprising a member adapted to bemoved in one direction to open the damper and in the opposite directionto close the damper, power means actmg on said member and tendin to movesaid member in a damper opening direction, said power means of itselfbeing insuflicient to move said member in a damper opening direction, afirst heat responsive motor energizable to assist sald power means tomove the member in a damper opening direction, a latch for holding themember in open damper position, a second heat motor energizable foractuating said latch into latching relation with said member, anelectrical circuit including a thermal responsive switch and electricalswitch means in series therewith, said electrical switch means beingactuated as the member approaches damper open position to complete thecircuit through the second heat motor and break the circuit through thefirst heat motor whereby, when the thermal responsive switch is closed,the latch is moved into engagement with said member to hold the memberin open damper position, said electrical switch means being actuated asthe member moves in a damperclosin direction to complete the circuitthrough the first heat motor and break the circuit through the secondheat motor, said thermal responsive switch responding to a use intemperature to break the circuit tosaid second heat motor whereby thelatch is released and the member moves in a damper closing direction,said thermal switch responding to a fall in temperature to close thecircuit to said electrical switch means and, when the member is indamper closing position, to close the circuit to said first heat motorwhereby said first heat motor is energized and supplements the power ofsaid power means to move said member in a damper opening direction. ,1 y

2. The furnace damper control mechanism defined in claim 1 wherein saidmember comprises a lever pivotally supported between its ends and oneend of which has an operative connection with said first heat motor andthe other end of which is adapted for engagement with said latch forholding the lever in damper open position.

3. A furnace damper control mechanism comprising a lever supportedbetween its ends and adapted to swing in one direction to open thedamper andi-in the opposite direction to close the damper, forceapplying means acting on one end of said lever and tending to swing thelever in the damper opening direction, said force applying means beingincapable of itself to swing said lever in the damper opening direction,a first heat responsive motor operatively connected with one end of saidlever and energizable to assist said force applying means to swing thelever in a damper opening direction, a latch for holding the 1 lever inopen damper position, a second heat motor energizable for actuating saidlatch into latching relation with said lever, an electrical circuitincluding a thermal responsive switch and electrical switch means inseries circuit therewith, said electrical switch means being actuated asthe lever swings in damper opening direction to complete the circuitthrough the second heat motor and break the circuit through the firstheat motor whereby, when the thermal responsive switch is closed, thelatch is moved into engagement with said lever to hold said lever inopen damper position, said electrical switch means being actuated as thelever swings in a damper closing direction to complete the circuitthrough the first heat motor and break the circuit through the secondheat motor, said thermal responsive switch responding to a rise intemperature to break the circuit to said second heat motor whereby thelatch is released and the lever moves in a damper closing direction,said thermal responsive switch responding to a fall in temperature toclose the circuit to said electrical switch means and, when the lever isin damper closing position, to close the circuit to said first heatmotor whereby said first heat motor sup- 'plements the force applied bysaid force applying means to move said lever in lamper openingdirection.

4. The furnace damper control mechanism defined in claim 1 wherein saidmember comprises a lever pivotally supported between its ends, saidpower means comprising a spring acting on said lever and tending toswing gthe lever in one direction about its pivotal support, said leverhaving one end thereof connectable with the damper to be controlled,said first heat motor having an ,operative connection with one end ofsaid lever.

CLARENCE F. ALBAN. RAYMOND H. MATTHEWS.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS

